[Bug 5023] Relationship between identity constraints and assertions

http://www.w3.org/Bugs/Public/show_bug.cgi?id=5023

           Summary: Relationship between identity constraints and assertions
           Product: XML Schema
           Version: 1.1 only
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Structures: XSD Part 1
        AssignedTo: cmsmcq@w3.org
        ReportedBy: dret@berkeley.edu
         QAContact: www-xml-schema-comments@w3.org


With the introduction of assertions in XSDL 1.1 there now is an overlap in
functionality between identity constraints and assertions. Both constructs have
very similar use cases, but work a little bit differently. The most important
difference is that identity constraints are defined in the context of elements,
and assertions in the context of types. This makes them behave very differently
in the presence of type derivation. While the specification is not a tutorial,
I think that the relationship (and the differences) should be made more
explicit.

I also would recommend XSDL 1.1 authors to avoid identity constraints
completely and only use assertions, which are better integrated into the data
model. But this kind of comment is probably is more appropriate for a tutorial
or a best practices document.

Received on Wednesday, 5 September 2007 17:10:02 UTC